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MPCMM0002 CMM—Backplane Considerations
Intel NetStructure
®
MPCMM0002 Chassis Management Module
Hardware TPS July 2007
30 Order Number: 309247-004US
6.2.3 Filter Tray
The CMM also provides direct support for a filter tray. The CMM provides signals to
handle a filter presence switch, two thermistors, and a tricolor LED.
The filter presence switch is typically a mechanical switch that connects the AF_PRES#
signal to ground when an air filter is installed in the chassis. The switch is debounced in
software.
The two thermistor inputs provide redundant temperature readings to the CMM. The
thermistors should be a NTC (negative thermocouple) device like the US Sensor*
USX2257 thermocouple (http://www.ussensor.com/). For maximum accuracy, a
dedicated logic ground reference signal AFTREF is provided to isolate localized
perturbations to logic ground. Chassis designers should use the AFTREF signal
exclusively for these thermocouples and should route the two temperature signals and
the reference signal in close proximity.
6.2.4 Power Switch
The CMM has support for an optional soft power switch. This dual-pole input signal can
be used to signal the CMM to gracefully shut down the elements within the chassis.
Both poles of this switch are debounced in software. If only one contact on the switch
closes, the CMM flags this as an error and generates a system event log entry.
These direct drive capabilities of the CMM are summarized in the table below. All the
outputs are protected via OR-ing diodes, as shown in Figure 12.
Figure 12. CDM Power Input
CDM 1 CDM 2